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Near-Field Communication Group #31

Near-Field Communication Group #31. Keshav Bansal Dan Hvala Tyler Rossi. Introduction. NFC is a short-range wireless technology. NFC provides unique advantages over other available wireless technologies.

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Near-Field Communication Group #31

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  1. Near-Field CommunicationGroup #31 Keshav Bansal Dan Hvala Tyler Rossi

  2. Introduction • NFC is a short-range wireless technology. • NFC provides unique advantages over other available wireless technologies. • The design includes a near-field transmitter and receiver to send data from one computer to another

  3. Benefits & Features • Not restricted to 1-to-1 communication • Multiple devices in a small area can communicate with each other using the same frequency. • Maximum transfer bit rate of 800kbps. • No special software is required. • Operation at a frequency of 13.5 MHz • No ethical concerns due to range

  4. Modulation/Demodulation Scheme • Frequency Shift Keying (FSK) • VCO produces a frequency-modulated signal at the transmitter • Phase lock loop demodulates the signal at the receiver.

  5. System Overview • Hardware • Transmitter • PC interface (MAX232A) • Voltage-Controlled Oscillator (POS+25) • Power Amplifier (LM6181) • Loop Antenna • Receiver • Loop Antenna • Amplifier (LM6181) • Phase Lock Loop (NE564) • PC interface (MAX232A)

  6. System Overview

  7. Pictures

  8. System Overview(Schematic)

  9. PC Interface • Connects through serial cable • Received by MAX232A • 0 to 5V square wave • Voltage divider • Non-inverting voltage adder

  10. PC Interface(Schematic)

  11. MAX232A Input/Output

  12. Voltage Controlled Oscillator • Operates on a 12-V power supply • Accepts an input from 3.7V to 4.2V from the PC interface. • Outputs a signal whose frequency varies according to the input voltage level

  13. VCO Output

  14. Power Amplifier • Accepts an input from the VCO • Outputs the signal to the loop antenna • Power gain of approximately 11dB

  15. Power Amplifier(Schematic) Vout Vin

  16. Amplifier Input/Output

  17. Loop Antenna • Loop Diameter = 6.5 cm • Inductance = 3 uH • Capacitor used to resonate the antenna at 13.5 MHz = 45 pF

  18. Loop Antenna • Very directional • Larger loop = more gain • Picks up less noise • Small, multi-loop turn does not radiate much

  19. Frequency Comparisons

  20. Phase Lock Loop • Tracks the frequency and phase of the input • Frequency of an FSK signal changes according to the data bits; therefore, PLL can demodulate an FSK signal. • Output is the VCO control voltage.

  21. Phase Lock Loop(Block Diagram)

  22. Phase Lock Loop Tracking

  23. Band-Pass Filters(Eliminated) • Tuned to 10MHz and 13.5MHz • Pass-band of 2-3MHz • Signal did not decay fast enough outside of the pass-band

  24. Difficulties • Small antenna bandwidth made us to revise our original design. • Drift in the frequency of VCO. • Amplifier oscillation • Most significant bit flipping

  25. Future Hardware Development • Less power consumption • More efficient loop antenna for larger range. • Smaller setup • Two-way communication

  26. Analysis • Strengths • No interference due to decaying fields • Within FCC regulation • FCC requires max E-field of 334uV/m at 30m • Our max E-field at 30m is 180uV/m • Weaknesses • Very small range • Sensitive to distance and alignment • 653mW

  27. Results • Maximum bit rate of 800kbps • Text communication between two PCs • Transmission range of 30cm • Ability to send a text file between PCs

  28. Credits • Ethan Miller • Dr. Ada Y. Poon • Dr. Christopher Schmitz • Dr. Steven Franke • Workers in the ECE Parts Shop

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